niu: remove one compound_head() call

After a "page = alloc_page(mask);", we do not need to use
compound_head() : page already points to the right place.

This would be true even if using alloc_pages().

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>